OBJECTIVE To assess frequency of urodynamic abnormalities in young men with chronic lower urinary tract symptoms (LUTS). METHODS We assessed 456 men (18-40 years old) with chronic LUTS. Those with the history of urogenital malignancies, neurological disease, urethral stricture or trauma, acute UTI, congenital urological disease, and diabetes mellitus were excluded. Patients were classified by special urodynamic diagnosis. RESULTS Mean patient age was 25.8  ±  5.9 years old and the mean symptom duration was 12.3 ±  3.2 months. Urodynamic studies showed bladder neck dysfunction in 96 of cases (21%), dysfunctional voiding in 69 (15.1%), detrusor overactivity in 62 (13.6%), small cystometric capacity in 49 (10.7%), and acontractile detrusor in 48 (10.5%), underactive detrusor in 11 (2.4%), low compliance in 18 (3.9%), detrusor overactivity plus acontractile detrusor in 6 (1.3%), low compliance plus small cystometric capacity in 5 (1.0%), detrusor overactivity plus small cystometric capacity together with low compliance in 4 (0.8%), low compliance plus Underactive detrusor in 3 (0.6%) and normal urodynamics in 85 (18.6%). Mean Q(max) in patients with bladder neck dysfunction, dysfunctional voiding, underactive detrusor, acontractile detrusor, underactive detrusor plus low compliance, and acontractile detrusor plus detrusor overactivity were lower than those of the other groups. Mean postvoid residues in patients with underactive detrusor, and underactive detrusor plus low compliance, were higher than those in the remaining groups. Positive four-glass test in patient with normal urodynamic was greater than those in the remaining groups. CONCLUSIONS A few clinical symptoms or noninvasive tests were useful in young men with chronic LUTS; hence, urodynamics are advised to make the correct diagnosis in this regard.